This invention relates to the continuous molding of fastener products, such as those having a multiplicity of miniature fastening elements extending from a common sheet-form base.
Touch fastener products have arrays of miniature fastener elements (for instance, hook-shaped or mushroom-shaped elements) extending from a common base. Typically, in order to be capable of engaging a loop fiber or another fastener element, these fastener elements have overhanging xe2x80x9ccrooksxe2x80x9d, such as the hook portion of a hook-shaped element or the underside of the head of a mushroom-shaped element. These crooks snag and retain loop fibers, for instance, to form a fastening, but can be challenging to mold in their fully functional form in non-opening mold cavities.
One solution for continuously molding such fastener elements for touch fasteners and other products was disclosed by Fischer in U.S. Pat. No. 4,794,028 (the full disclosure of which is hereby incorporated herein by reference as if fully set forth). In commercial implementations of his solution, a cylindrical, rotating mold roll is composed of a large number (e.g., thousands) of thin, disk-shaped mold plates (or rings) and spacer plates which are stacked concentrically about a central barrel. Extending inwardly from the periphery of the mold plates are cavities for molding the hook elements. Molten resin is introduced to the rotating mold roll and forced into the cavities to form the fastener elements while a layer of the resin on the circumference of the roll forms the integral strip-form base. The mold roll is cooled (e.g., by circulating a liquid coolant through the barrel) to sufficiently solidify the fastener elements to enable them to be stripped from their cavities before making a complete revolution about the mold roll. Thus, in prior implementations of the Fischer process the production speeds obtainable for a given diameter mold roll have been limited by the required xe2x80x9cresidence timexe2x80x9d of the cooling fastener elements in their cavities to enable successful withdrawal. Over-chilling the mold roll to reduce the required residence time can impede proper filling of the cavities by solidifying the resin as it is forced into the cavities.
Another implementation of the general Fischer process, also using stacked mold plates in the form of a multi-plate mold roll apparatus for continuously molding fastener products is described by Murasaki et al. in U.S. Pat. No. 5,441,687.
Multi-plate mold rolls are more prone to bending deflection caused by molding pressures than solid rolls of similar diameter. Such bending deflection can result in undesirable base thickness variation across the width of the fastener product at higher molding pressures.
In U.S. Pat. No. 3,594,863 George Erb discloses a different method and apparatus for molding hook-type fastener elements without employing a mold roll. Erb forms his hooks in cavities partially defined by grooves cut into a moving belt, by injecting molten nylon against the belt (i.e., from the xe2x80x9chook sidexe2x80x9d of the resulting product), thereby forming narrow ribbons, each ribbon having only two rows of hooks, one row extending from each of its longitudinal edges. To form a useful sheet of fastener product having an entire two-dimensional array of hooks (i.e., of many rows of hooks), Erb laminates many individual ribbons to a preformed base sheet.
We have realized that touch fastener products, with either hook-type or mushroom-type fastener elements integrally molded with a solid base and arranged in wide arrays, can be formed in a continuous process by molding the fastener elements and base together on a moving belt defining an entire array of cavities.
According to a first aspect of the invention, a method is provided for continuously forming a fastener product having an array of fastener elements extending from a continuous, sheet-form base. The method includes the steps of:
(1) providing a mold belt defining a two-dimensional array of cavities extending from an outer surface of the belt;
(2) training the mold belt in a loop about first and second rolls;
(3) introducing molten plastic resin to the outer surface of the mold belt;
(4) forcing the plastic resin into the cavities of the belt under pressure in a gap to fill the cavities while forming the sheet-form base of the product on the outer surface of the belt;
(5) solidifying the resin as the resin is carried on the belt; and then
(6) stripping the solidified resin from the mold belt, the mold belt continuing along its loop and returning to the gap.
In some embodiments, the cavities of the belt are shaped to mold hook-type fastener elements having distal ends extending toward the sheet-form base. In some other embodiments, the cavities of the belt are shaped to mold mushroom-type fastener elements having heads overhanging the sheet-form base in multiple directions.
Preferably, the cavities of the belt are sized to mold fastener elements of less than about 0.050 inch in total height, as measured from the product base (more preferably, less than about 0.020 inch in total height).
In some embodiments, the mold belt includes a belt-form substrate and plating material deposited upon one side of the substrate in a predetermined pattern to form the fastener element-shaped cavities.
In some cases, the cavities of the mold belt extend only partially through the mold belt.
In some arrangements, the plastic resin is forced into the cavities under pressure at a nip defined between the first roll (which may be driven) and a pressure roll.
In some embodiments, the method also includes cooling the mold belt away from the gap.
In some embodiments, the cavities of the mold belt extend completely through the mold belt.
For some applications, the method also includes timing the mold belt to the first roll such that the cavities of the mold belt align with dimples in the surface of the first roll. The step of forcing plastic resin into the cavities includes filling the dimples of the first roll through the aligned cavities to form fastener element heads while forming corresponding fastener element stems in the aligned belt cavities.
In some other embodiments, the method includes timing the mold belt to the first roll such that the cavities of the mold belt align with protrusions extending from the surface of the first roll. The protrusions extend into the aligned cavities as the resin is forced into the cavities, to form fastener elements with heads defining top recesses formed by the protrusions.
In some configurations, the step of stripping the solidified resin from the mold belt includes passing the belt about the second roll, the second roll having projections arranged to push the resin from the belt cavities. The second roll is timed to the mold belt to align the projections with the belt cavities.
In some cases, the gap is defined adjacent the first roll, such as between the first roll and a pressurized extruder.
In some embodiments, the method includes introducing a backing material to the resin in the gap, whereby the backing material is laminated to one side of the sheet-form base of the product.
In some cases, the method includes cooling the resin as it is carried on the belt.
The mold belt comprises metal in some instances, the cavities forming holes extending through the belt.
In some arrangements, the belt includes solidified resin molded to define the cavities.
In some embodiments, the belt has a series of rigid mold plates, each mold plate having an exposed edge defining a row of the cavities. The mold plates are spaced apart and held together by flexible resin in the form of a continuous belt.
According to a second aspect of the invention, a method is provided for continuously forming a fastener product having an array of fastener elements extending from a continuous, sheet-form base. The method includes the steps of:
(1) providing a mold belt defining an array of cavities extending from an outer surface thereof;
(2) training the mold belt about first and second rolls;
(3) forcing molten plastic resin into the cavities of the belt under pressure to fill the cavities in a pressure region while forming the sheet-form base of the product on the outer surface of the belt;
(4) cooling the resin as the resin is carried on the mold belt; and thereafter
(5) stripping the cooled resin from the mold belt at a stripping region spaced apart from the pressure region, the mold belt returning to the pressure region along a predetermined path.
In some cases, the pressure region is defined between a pressurized extruder and a pressure reaction plate. In some other cases, the pressure region is defined between a pair of rolls, the molten resin being introduced to the mold belt under atmospheric pressure before being forced into the cavities in the pressure region.
In some instances, the pressure zone is defined between a pressurized extruder and the first roll, the second roll being disposed diametrically opposite the pressure zone and arranged to apply load to the first roll through a load transfer roll to balance bending loads applied to the first roll by extruder pressure.
According to a third aspect of the invention, a method of continuously forming a fastener product having an array of fastener elements extending from a continuous, sheet-form base, includes the steps of:
(1) providing a mold belt defining an array of holes extending therethrough from one broad surface of the belt to an opposite broad surface of the belt;
(2) in a pressure region, forcing molten plastic resin into the holes of the belt under pressure from the one broad surface while the holes are covered at the opposite broad surface of the belt by a pressure reaction surface, to fill the holes while forming the sheet-form base of the product on the one broad surface of the belt;
(3) solidifying the resin as the resin is carried away from the pressure reaction surface on the mold belt; and thereafter
(4) stripping the solidified resin from the mold belt at a stripping region spaced apart from the pressure region.
In some embodiments, the mold belt is in the form of a continuous loop, the mold belt returning to the pressure region from the stripping region.
In some cases, the resin is solidified by being cooled while carried on the belt.
The solidified resin is pushed from the holes of the belt at the stripping region, in some embodiments, by aligned projections extending from a roll about which the belt is trained.
According to a fourth aspect of the invention, a method of making a mold belt for the continuous molding of a fastener product having an array of molded fastener elements extending from a continuous, sheet-form base, includes the steps of:
(1) providing a mold master surface having an array of projecting, male fastener elements extending from the master surface;
(2) casting mold resin about the fastener elements on the mold master surface;
(3) solidifying the mold resin; and then
(4) stripping the solidified resin from the mold master surface, leaving an array of female cavities extending into the solidified resin from a surface thereof, the cavities having the shape of the fastener elements of the mold master surface.
In some cases, the resin is cast about reinforcement elements which may comprise metal.
Suitable resins include thermoset materials.
In some embodiments, the fastener elements of the mold master surface are hook-type fastener elements.
In some cases, the step of casting includes sequentially forming longitudinal sections of a flexible mold belt in a section molding cavity, each successive longitudinal section being formed at an end of a previously formed section.
According to a fifth aspect of the invention, a method of making a mold belt for the continuous molding of a fastener product having an array of molded fastener elements extending from a continuous, sheet-form base, includes the steps of:
(1) providing a continuous, flexible, strip-form belt adapted to be trained about multiple rolls; and
(2) forming an array of holes through the belt, each hole shaped to form a fastener element having an overhanging head for engaging loops.
In some embodiments, the belt comprises metal, the holes being formed through the metal of the belt by an etching process. The belt may be etched from opposite surfaces of the belt to form holes extending completely through the belt.
In some cases, the holes so formed are shaped to mold hook-type fastener elements.
According to a sixth aspect of the invention, a method of making a mold belt for the continuous molding of a fastener product having an array of molded fastener elements extending from a continuous, sheet-form base, includes the steps of:
(1) providing a series of flat mold plates, each mold plate having an edge and defining a row of fastener element-shaped cavities extending from the edge;
(2) arranging the mold plates in parallel, spaced apart relation, the edge of each mold plate from which its cavities extend facing in a common direction; and
(3) injecting elastomeric material into spaces defined between the mold plates to connect the mold plates and form a flexible length of belt.
In some embodiments, the mold plates each define apertures therethrough. The step of injecting includes filling the apertures with the elastomeric material to interconnect elastomeric material on both sides of each mold plate. In some cases, before the step of injecting, reinforcement wire is strung through the apertures of adjacent mold plates, the reinforcement wire being subsequently encapsulated by the elastomeric material.
The method includes, in some cases before the step of injecting, filling the cavities of the mold plates with a removable filler to prevent the cavities from filling with elastomeric material during the injecting step. After the step of injecting, the filler is removed from the cavities.
In presently preferred embodiments, the mold plates are composed of metal and the elastomeric material comprises heat-resistant rubber, silicone or urethane. The mold plates each have a thickness of less than about 0.020 inch, a length of at least about 0.5 inch, and a width, corresponding to mold belt thickness, of between about 0.040 and 0.25 inch, and are spaced apart to define interplate gaps of between about 0.005 and 0.025 inch.
In some cases, each mold plate has a back edge, on a side opposite the cavities, which is exposed on a back side of the belt for transferring heat from the cavities.
According to a seventh aspect of the invention, an apparatus is provided for continuously molding a fastener product having an array of fastener elements integrally molded with and extending from a continuous, strip-form base, the apparatus includes first and second rolls, a flexible mold belt defining an array of fastener element-shaped cavities extending from an outer surface of the belt, the mold belt trained about both the rolls, and a source of molten plastic resin arranged to deliver resin to the mold belt. The apparatus is constructed to force the plastic resin into the fastener element-shaped cavities of the belt under pressure in a gap to mold the array of fastener elements while forming the strip-form base of the product.
Various embodiments of the apparatus of the invention contain one or more of the characteristics described above with respect to the method aspects of the invention.
In some embodiments, the apparatus includes a pressure roll adjacent the first roll, the pressure and first rolls defining therebetween a nip in which the plastic resin is forced into the cavities under pressure.
In some configurations, the apparatus includes a cooling system adapted to cool the belt away from the gap.
Presently preferred belts have a thickness of less than about xe2x85x9 inch (more preferably less than about 0.050 inch, and even more preferably less than about 0.020 inch), and a width of at least about xc2xd inch (more preferably of at least about 2 inches, and een more preferably of at least about 6 inches), for molding a fastener product of a corresponding width.
In some cases, the mold belt consists essentially of molded thermoset resin.
In some other cases, the mold belt comprises a laminate having a layer of metal and a layer of thermoset resin, the fastener element-shaped cavities being defined in the layer of thermoset resin.
In yet other cases, the mold belt comprises molded thermoset resin and reinforcing elements extending the length of the mold belt. Suitable reinforcing elements include cables, wires, mesh, strips or yarns.
In some embodiments, the mold belt consists essentially of metal, the fastener element-shaped cavities comprising holes extending through the mold belt between two opposite broad sides of the belt.
In some embodiments, the mold belt includes a layer of metal bonded to a layer of elastomeric material, the elastomeric material being sufficiently soft to enable the elastomeric material to be radially compressed by cavity pressure to locally and temporarily enlarge the effective diameter of the fastener element cavities within the layer of elastomeric material.
Some mold belts include a series of flat mold plates, each mold plate having an edge and defining a row of fastener element-shaped cavities extending from the edge, and elastomeric material separating and interconnecting the mold plates in parallel, spaced apart relation to form a flexible length of belt. The edge of each mold plate from which its cavities extend faces in a common direction.
In some configurations, the mold plates each define apertures through the plate, the apertures filled with the elastomeric material to interconnect elastomeric material on both sides of each mold plate. In some cases, the mold belt includes reinforcement wire extending through the apertures of adjacent mold plates and encapsulated within the elastomeric material.
In presently preferred embodiments, the mold plates are composed of metal. Suitable elastomeric materials include compounds of heat-resistant rubber, silicone or urethane. Preferably, the mold plates each have a thickness of less than about 0.020 inch, a length of at least about 0.5 inch, and a width, corresponding to mold belt thickness, of between about 0.040 and 0.25 inch, and are spaced apart to define interplate gaps of between about 0.005 and 0.025 inch.
In some other embodiments, the mold belt has an array of rigid inserts interconnected by a strip of flexible resin, each insert defining a corresponding cavity of the array of cavities. Presently preferred insert materials include metal. The rigid inserts may extend through the thickness of the mold belt, and each of the cavities may extend through the thickness of the mold belt. In some cases, surfaces of the inserts defining the cavities are of stamped form. The cavities may be shaped to form mushroom-type fastener elements having overhanging heads at the distal ends of stems.
In some embodiments, the source of molten plastic comprises a pressurized extruder. The gap is defined, in some cases, between the first roll and the pressurized extruder, or between the pressurized extruder and a fixed pressure reaction plate.
In some configurations, the apparatus is constructed to introduce a backing material to the resin in the gap, whereby the backing material is laminated to one side of the sheet-form base of the product.
The cavities of the belt are defined, in some embodiments, by etched surfaces.
According to an eighth aspect of the invention, an apparatus is provided for continuously molding a fastener product having an array of mushroom-type fastener elements integrally molded with and extending from a continuous, strip-form base. The apparatus includes first and second rolls; a flexible mold belt defining an array of holes extending through the belt, the mold belt trained about both the rolls; a source of molten plastic resin arranged to deliver resin to the mold belt; means of stripping the base and preform stems from the belt; and means of reforming resin of a distal end of each preform stem to form an overhanging head on each stem, thereby forming the array of mushroom-type fastener elements. The apparatus is constructed to force the plastic resin into the holes of the belt under pressure in a gap to mold an array of preform stems while forming the strip-form base of the product.
According to a ninth aspect of the invention, an apparatus is provided for continuously molding a fastener product having a wide array of fastener elements extending from a continuous, strip-form base, the apparatus including first and second rolls; a mold belt defining an array of cavities extending from an outer surface of the belt in at least three rows, the mold belt trained about both the first and second rolls; a source of molten plastic resin arranged to deliver resin to the outer surface of the mold belt; means for cooling the resin in the cavities of the belt to solidify the resin while on the belt; and means for stripping the cooled resin from the belt, the fastener elements pulled complete from the belt cavities. The apparatus is constructed to force the plastic resin into the cavities of the belt under pressure to fill the cavities as the continuous base of the product is formed on the outer surface of the mold belt.
Various embodiments of this aspect of the invention contain one or more of the features of above-described embodiments of other aspects of the invention.
In some embodiments, the source of molten plastic resin includes a pressurized extruder.
In some configurations, the extruder is arranged to extrude the resin into the cavities of the mold belt in a gap defined between the first roll and the extruder.
In some other configurations, the extruder is arranged to extrude the resin into the cavities of the mold belt in a gap defined between the extruder and a pressure reaction plate disposed between the first and second rolls.
In some embodiments, the cooling means comprises a fan arranged to force air across the mold belt.
In some embodiments, the cooling means includes coolant circulated through at least one roll about which the mold belt is trained.
In some cases, the cavities of the mold belt are shaped to form fastener elements having overhanging heads.
In some other cases, the cavities of the mold belt are shaped to form fastener element stems. The first roll defines an array of cavities at its peripheral surface shaped to form fastener element heads, and has a series of pins extending from its peripheral surface to engage corresponding holes in the mold belt for timing the belt with respect to the first roll to align the cavities of the mold belt with the cavities of the mold roll to form an array of contiguous fastener element-shaped cavities. The molten plastic resin fills the array of contiguous cavities at the first roll to form the array of fastener elements.
The invention represents a significant improvement over conventional roll-forming machines and techniques, in many respects. By removing the mold cavities from the circumference of a single roll, the cavities can be advantageously circulated through cooling processes. The forming fastener elements are also afforded longer residence times, decreasing the rate at which they must be cooled and enabling greater crystallization during solidification. This can enable, in turn, lower cavity filling pressures even at relatively high production rates. In addition, the invention enables the use of solid rolls which more robustly resist bending loads than multi-plate rolls. The mold belt can be readily removed from the molding apparatus for cleaning and replacement, and is useful for forming, in one simple molding step, complete fastener products having a wide array of fastener elements all extending from a single, continuous, strip-form base. Many of the belt structures featured in the invention are inexpensive enough to produce that they may be considered disposable if their cavities become plugged.
These and other advantages and features will be understood from the following description, drawings and claims.